Stress-induced catecholamine changes in the hemolymph of the oyster Crassostrea gigas

The stress response is a series of coordinated physiological reactions increasing an organism's capacity to maintain homeostasis in the presence of threatening agents. This fundamental process is known to involve hormonal signaling to rapidly modulate key physiological functions in vertebrates, but data are lacking concerning neuroendocrine responses to stress in invertebrates. The present study examined circulating catecholamine (CA) responses to stress in oysters. Mechanical disturbances (consisting of shaking the animals) and temperature or salinity variations were applied to the animals because these three types of stressors are commonly encountered by oysters in aquaculture or in their natural habitat. Results show that both circulating noradrenaline (NA) and dopamine (DA) concentrations increased in response to stress. The catecholaminergic response to acute mechanical stressors was rapid (less than 5 min), transient (a return to basal CA levels was observed after 60-90 min), and reflected both the intensity and duration of the perturbation. In contrast, responses to temperature and salinity variations were long lasting (up to 72 h). CA concentrations varied from 1.61 +/- 0.30 ng NA/ml and 0.41 +/- 0.05 ng DA/ml to maximal values of 22.07 +/- 0.97 ng NA/ml and 2.24 +/- 0.19 ng DA/ml. Such CA concentrations are known to induce physiological responses in bivalves, suggesting that stress-induced NA and DA changes exert a regulatory function in oysters.